Mild head injury and speed of information processing: A prospective study of professional rugby league players

Abstract

The sensitivity of several short tests of speed of information processing to the effects of mild head injury in rugby league football was investigated. The measures used were the Symbol Digit Modalities Test, the Digit Symbol Substitution Test, and the Speed of Comprehension Test. Two studies were conducted, the first to examine the effect of practice, the second to determine sensitivity to cognitive impairment immediately following injury. The first study established alternate form equivalence and demonstrated that performance on the Speed of Comprehension and Digit Symbol Substitution tests improved with practice, whereas the Symbol Digit Modalities test remained stable. A second study of 10 players who subsequently sustained mild head injuries showed that measures of speed of information processing were sensitive to impairment in the postacute phase, whereas an untimed task of word recognition (Spot-the-Word) was not. Speed of Comprehension was more sensitive to postinjury impairment than either the Digit Symbol Substitution or Symbol Digit Modalities tests. A repeated baseline assessment before injury using the higher score to reflect a player's potential, allowed measurement of impaired performance on sensitive tests.     

Deficits in auditory P50 inhibition in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is considered to involve abnormalities in inhibitory processes including gating systems. Auditory P50 inhibition, which is assessed by using a paired auditory stimulus paradigm to record P50 mid-latency evoked potential, is assumed to reflect sensory gating. In the present study, we investigated auditory P50 inhibition in subjects with OCD, and examined the relationship between P50 and clinical variables or neuropsychological performance. Twenty-six subjects with OCD and 26 age- and sex-matched healthy controls received P50 recording and neuropsychological tests. In the OCD subjects, we also evaluated clinical features including OC symptoms and subtypes of the disorder. P50 T/C ratios were significantly higher in OCD subjects than in control subjects (t=2.9, df=50, p=0.006). Compared to the controls, the OCD subjects performed significantly worse on the Symbol Digit Modalities Test (SDMT) and the Trail Making Test (TMT). There were no correlations between P50 T/C ratios and clinical variables or the results of neuropsychological tests. Our findings suggest that sensory gating deficits may be involved in the pathophysiology of OCD in a different way from clinical symptoms and executive attention dysfunction.     

Information processing difficulty long after self-reported concussion.

Recovery of cognitive function after mild head injury (MHI) is thought to be relatively swift and complete. The present study replicates and extends previous work in which university students with self-reported concussion demonstrated reduced P300 amplitude on a set of easy and difficult attention tasks, in addition to performing more poorly than controls on demanding cognitive tasks many years after injury. In the present study, 13 students with self-reported concussion (MHI group: M time since injury = 8 years) and 10 controls were matched for age, sex, education, and a variety of cognitive, physical and emotional complaints. Controls outperformed the MHI group on the Digit Symbol substitution task and on a difficult dual task involving tone discrimination and visual working memory. Additionally, controls exhibited larger P300 amplitudes on both an easy and a difficult auditory discrimination task. A combination of electrophysiological, neuropsychological and self-report indices predicted group membership (MHI vs. control) with 88% accuracy. The present results, coupled with previous work, offer preliminary evidence that the combination of event-related potentials and demanding behavioral measures might reveal long-lasting, subtle cognitive problems associated with MHI. These findings may challenge existing notions of complete recovery after MHI.     

Neuropsychological deficits in symptomatic minor head injury patients after concussion and mild concussion.

Recent studies have concluded that most individuals who sustain minor head injury are free of persistent neuropsychological dysfunction. Nevertheless, a subgroup of patients experience continuing post-concussive difficulties and neuropsychological deficits. This study examined 53 symptomatic minor head injury patients referred for neuropsychological evaluation between one and 22 months after injury. These individuals performed significantly poorer than uninjured controls on four of eight neuropsychological tests. Patients who lost consciousness during injury obtained test scores similar to persons who experienced disorientation or confusion but no loss of consciousness. The results indicate that minor head injury patients who report post-concussive symptoms possess measurable neuropsychological deficits and the severity of these deficits is independent of neurological status immediately following injury.     

Motivation and neuropsychological test performance following mild head injury

Effect of motivation on neuropsychological test performance in mild head injury was assessed. Motivation was measured using the Portland Digit RecognitionTest. Three groups were compared: (a) mildhead injury, financial incentives, good motivation; (b) mild head injury, financial incentives, poor motivation; (c) moderate/severe head injury, good motivation. The neuropsychological battery included measures of sensory function, motor function, attention, intelligence, abstract reasoning, and memory. Mild head injury well motivated patients performed significantly better than the other two groups on some tests. Mild head injury poorly motivated individuals and moderate-severe head injury patients were indistinguishable on many tests. Consistent with previous reports, tactile sensory (finger recognition and Fingertip Number Writing Perception) and recognition memory (Rey Auditory Verbal Learning) tasks were identified as clinically useful measures of poor motivation. On these measures mild head injury well motivated examinees performed no better than moderate-severe patients, with both groups superior to mild head injury poorly motivated examinees. Sensitivity and specificity data are reported. Our measures of tactile sensation and verbal recognition memory were more affected by motivation than by the severity of head injury.     

No association between prepulse inhibition of the startle reflex and neuropsychological deficit in chronic schizophrenia

Sensorimotor gating deficits are relevant in schizophrenia and can be measured using prepulse inhibition (PPI) of the startle reflex. It is conceivable that such deficits may hinder the cognitive functions in schizophrenia patients. In this study, using PPI and a neuropsychological battery, we studied this possibility in a group of 23 acute, neuroleptic-free schizophrenia patients and 16 controls. A non-significant decrease in PPI was found in the patients as compared to the controls, as well as significant differences in the performance of Trail A and B in Wisconsin Card Sorting and Digit/Symbol Tests. No statistically significant correlations between PPI and neuropsychological performance were found after the correction for multiple comparisons in any group. Our results suggest that PPI deficits in schizophrenia patients may not contribute to the cognitive deficits typical of that illness, at least in patients with a non-significant PPI decrease.     

Recovery from visual and acoustic hyperaesthesia after mild head injury in relation to patterns of behavioural dysfunction.

Patients with head injuries frequently complain of a decreased ability to endure intense light and sound stimuli. The few psychophysical studies that have objectively studied this type of hyperaesthesia have not assessed to what extent patients recover from this hyperaesthesia after mild head injury (MHI). A computerised rating technique was used to assess tolerance to intense sound (95 dB) and light (1500 lux) stimuli in patients with an uncomplicated MHI. Patients were tested 10 days and five weeks after the injury. Although most patients substantially recovered from both visual and acoustic hyperaesthesia, 25% of the patients were still not able to endure intense stimuli by five weeks. Analysis of data obtained with two behavioural rating scales (one with post-concussive/cognitive complaints and a second with emotional/vegetative complaints) indicated that visual hyperaesthesia was specifically related to the post-concussive/cognitive complaints scale.     

Neuropsychological prediction of conversion to Alzheimer disease in patients with mild cognitive impairment

CONTEXT: The likelihood of conversion to Alzheimer disease (AD) in mild cognitive impairment (MCI) and the "optimal" early markers of conversion need to be established. OBJECTIVES: To evaluate conversion rates to AD in subtypes of MCI and to identify neuropsychological measures most predictive of the time to conversion. DESIGN: Patients were followed up semiannually and controls annually. Subtypes of MCI were determined by using demographically adjusted regression norms on neuropsychological tests. Survival analysis was used to identify the most predictive neuropsychological measures. SETTING: Memory disorders clinic. PARTICIPANTS: One hundred forty-eight patients reporting memory problems and 63 group-matched controls. MAIN OUTCOME MEASURE: A consensus diagnosis of probable AD. RESULTS: At baseline, 108 patients met criteria for amnestic MCI: 87 had memory plus other cognitive domain deficits and 21 had pure memory deficits. The mean duration of follow-up for the 148 patients was 46.6 +/- 24.6 months. In 3 years, 32 (50.0%) of 64 amnestic-"plus" and 2 (10.0%) of 20 "pure" amnestic patients converted to AD (P = .001). In 148 patients, of 5 a priori predictors, the percent savings from immediate to delayed recall on the Selective Reminding Test and the Wechsler Adult Intelligence Scale-Revised Digit Symbol Test were the strongest predictors of time to conversion. From the entire neuropsychological test battery, a stepwise selection procedure retained 2 measures in the final model: total immediate recall on the Selective Reminding Test (odds ratio per 1-point decrease, 1.10; 95% confidence interval, 1.05-1.14; P < .0001) and Digit Symbol Test coding (odds ratio, 1.06; 95% confidence interval, 1.01-1.11; P = .01). The combined predictive accuracy of these 2 measures for conversion by 3 years was 86%. CONCLUSIONS: Mild cognitively impaired patients with memory plus other cognitive domain deficits, rather than those with pure amnestic MCI, constituted the high-risk group. Deficits in verbal memory and psychomotor speed/executive function abilities strongly predicted conversion to AD.     

Emergency department assessment of mild traumatic brain injury and prediction of post-concussion symptoms at one month post injury

Mild traumatic brain injury (mTBI) is a common injury and a significant proportion of those affected report chronic symptoms. This study investigated prediction of post-concussion symptoms using an Emergency Department (ED) assessment that examined neuropsychological and balance deficits and pain severity of 29 concussed individuals. Thirty participants with minor orthopedic injuries and 30 ED visitors were recruited as control subjects. Concussed and orthopedically injured participants were followed up by telephone at one month to assess symptom severity. In the ED, concussed subjects performed worse on some neuropsychological tests and had impaired balance compared to controls. They also reported significantly more post-concussive symptoms at follow-up. Neurocognitive impairment, pain and balance deficits were all significantly correlated with severity of post-concussion symptoms. The findings suggest that a combination of variables assessable in the ED may be useful in predicting which individuals will suffer persistent post-concussion problems.     

Double cross-validation and improved sensitivity of the rapid screen of mild traumatic brain injury

This study aimed to replicate and cross-validate the Rapid Screen of Concussion (RSC) for diagnosing mild TBI (mTBI). One hundred (81 male, 19 female) cases of mTBI and 35 (23 male and 12 female) cases of orthopaedic injuries were tested within 24 hr of injury. Double cross-validation was used to examine whether total RSC scores obtained in the current sample, generalised to one previously reported. In the new sample, mTBI patients answered fewer orientation questions, recalled fewer words on the learning trial and after a delay, judged fewer sentences in 2 min, and completed fewer symbols in the Digit Symbol Substitution Test than orthopaedic controls. The formulae and cut-offs developed on the original and new samples produced similar sensitivity and overall correct classification rates. Inclusion of the Digit Symbol Substitution Test performance of the new sample improved the sensitivity (80.2%) and specificity (82.6%) in males. It did not improve the correct classification rate in females, which was 89.5% sensitivity and 91.7% specificity before the inclusion of the Digit Symbol Substitution Test. Taken together, these results indicate that a combined score on this 12-min screen yields a measure of level of brain impairment up to 24 hr after mTBI.     

Neuropsychological evaluation of mild head injury.

Neuropsychological deficits following mild head injury have been reported recently in the literature. The purpose of this study was to investigate this issue with a strict methodological approach. The neuropsychological performance of 50 mildly head injured patients was compared with that of 50 normal controls chosen with the case-control approach. No conclusive evidence was found that mild head injury causes cognitive impairment one month after the trauma.     

Cerebrospinal fluid biomarkers and cognitive performance in non-demented patients with Parkinson's disease

We tested the hypothesis that levels of CSF biomarkers associated with dementia and cognitive impairment are correlated with cognitive performance in non-demented Parkinson's disease (PD) patients. Twenty-two non-demented patients with PD underwent neuropsychological testing and lumbar puncture to collect CSF. We correlated performance scores on the Logical Memory (delayed), Category Fluency, Digit Symbol, and Trails B minus A with CSF concentrations of amyloid (A) β(42), total tau (t-tau), Aβ(42)/t-tau, and Brain Derived Neurotrophic Factor (BDNF). We observed significant associations between performance on the Digit Symbol test and CSF levels of Aβ(42), Aβ(42)/t-tau, and BDNF, and between performance on the Category Fluency (vegetable) and Aβ(42)/t-tau. While several of these associations were attenuated by adjusting for age, our results suggest that it may be possible to use CSF biomarkers to characterize pathophysiologic processes underlying even mild cognitive deficits in non-demented PD patients.     

An investigation of attention,executive, and psychomotor aspects of cognitive fatigability

Objective: Self-perceived mental fatigue is a common presenting symptom in many neurological diseases. Discriminating objective fatigability from self-perceived mental fatigue might facilitate neuropsychological diagnosis and treatment programs. However clinically valid neuropsychological instruments suitable for assessment of fatigability are still lacking. The prime aim of the study was to investigate aspects of cognitive fatigability and to identify properties of neuropsychological tests suitable to assess fatigability in patients with persistent cognitive complaints after mild brain injury. Another aim was to investigate whether cognitive fatigability captured by neuropsychological measures is influenced by depression or sleep disturbances. Method: Twenty-four patients with persistent cognitive symptoms after mild traumatic brain injury (mTBI), (aged 18–51 years) and 31 healthy controls (aged 20–49 years) underwent neuropsychological testing measuring three cognitive fatigability domains: Attention fatigability was assessed using the Ruff 2 & 7 Selective Attention Test, executive fatigability using the Color Word Test (Stroop), and psychomotor fatigability using the Digit Symbol Substitution Test from the Wechsler Adult Intelligence Scale–Third Edition (WAIS–III). Subjective fatigue was measured using the Fatigue Severity Scale and a questionnaire of everyday consequences of fatigue. Depression was screened using the Hospital Anxiety and Depression Scale and sleep disturbances using the Pittsburgh Sleep Quality Index. Results: The patients reported significantly more mental fatigue and performed worse on tests of psychomotor and executive fatigability than the healthy controls. Furthermore, the cognitive fatigability measures were not influenced by depression or sleep disturbances, as was the case in self-reported fatigue. Conclusion: Tests demanding executive or simultaneous processing of several neuropsychological functions seem most sensitive in order to capture cognitive fatigability. Clinical tests that can capture fatigability enable a deeper understanding of how fatigability might contribute to cognitive complaints and problems in maintaining daily activities.     

Performance in the Stroop color word test in relationship to the persistence of symptoms following mild head injury

There is much controversy about whether the persistence of postconcussive symptoms (PCS) in mild head injured patients (MHI) is related to the presence of cognitive deficits. Most studies performed so far have relied on normal non-concussed control subjects rather than directly comparing patients with and without PCS following MHI. In addition, subtle cognitive deficits may be present in MHI patients that are demonstrable only with more demanding cognitive tasks. In the present study the Stroop Color Word Interference Test together with a more demanding modified interference subtask was administered to two groups of patients with uncomplicated MHI 10 days, 5 weeks and 3 months after the injury. Ten patients with persistent symptoms at 3 months were selected and individually matched with MHI patients who had initially reported symptoms but who had recovered by 3 months. The scores of the two retrospectively defined groups were compared at the different time points. Between-subjects analysis revealed overall differences for both the original and modified color word interference subtask. Within-subject analysis indicated that only the recovery rate in the modified interference subtask was significantly different between the two groups. The observation that there was a parallel trend between recovery and persistence of PCS and performance on the cognitive interference measures supports the notion that there is a functional relationship between these two phenomena.     

Glucose metabolic rate and progression of illness in Alzheimer's disease

Thirty-eight patients with mild to moderate Alzheimer's disease (AD) underwent a neuropsychological test battery and 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) before beginning and at the end of a randomized double-blind study of an experimental treatment. Twelve of the patients took placebo. In the placebo patients, Mini-Mental State (MMS) score decreased and cortical metabolism increased significantly over the 6-month course of the study. Correlations of metabolism with neuropsychological performance were stable over time in the placebo group. Cortical metabolism correlated significantly with performance on the Blessed Information Subtest and the MMS and showed trend correlations with performance on the WAIS Digit Symbol and Word Fluency. Patients with high relative occipital metabolism tended to do poorly on word fluency. Low baseline relative metabolism in right frontal cortex and high baseline relative metabolism in left parietal and temporal cortices and in right occipital cortex predicted more 6-month deterioration on the World Fluency Test, suggesting that frontal metabolic deficits may precede neuropsychological deficits. Correlations of 6-month change in MMS, Blessed and Digit Symbol performance with initial glucose metabolism were not significant.     

Annual rate and predictors of conversion to dementia in subjects presenting mild cognitive impairment criteria defined according to a population-based study

Elderly subjects diagnosed with mild cognitive impairment (MCI) are becoming the target of intervention trials. The criteria used for MCI are principally issued from prospective clinical studies, although longitudinal population-based studies having identified several cognitive predictors of dementia can be of great contribution in the definition of these criteria. This study was conducted to explore the external validity of MCI criteria issued from a longitudinal population-based study, and subsequently to identify the best predictors of the short-term conversion to Alzheimer's disease 2 years after the MCI diagnosis. Ninety elderly volunteers with memory complaint diagnosed with MCI on the basis of their functional and neuropsychological performances were followed up within 2 years. The potential predictors of the conversion to dementia collected at baseline included age, gender, educational level, size of temporal lobe, apolipoprotein E genotype and a series of neuropsychological measures (Mac Nair Scale, Mini-Mental State Examination, Benton Visual Retention Test, Isaacs Set Test, Digit Symbol Substitution Task, Letter Cancellation Task, digit span tasks and finger-tapping test). Within the 2 years, 29 subjects (32.2%) presented a conversion to dementia. The risk of conversion to dementia was associated with age and size of temporal lobe but not with gender, education, or apolipoprotein E4 genotype. Several neuropsychological measures were associated with the risk of conversion to dementia, but in a logistic regression performed with the significant variables found in the univariate analysis, only the Letter Cancellation Test was shown to be an independent predictor. In conclusion, the quite elevated conversion rates obtained show the usefulness, when defining MCI criteria, of considering not only memory impairment but also impairment in other cognitive areas, as well as mild impairment on higher-order activities of daily living. Among the variables considered, the Letter Cancellation Test proved to be a major predictor of short-term conversion to dementia.     

A study of persistent post-concussion symptoms in mild head trauma using positron emission tomography

BACKGROUND: Complaints of persistent cognitive deficits following mild head trauma are often uncorroborated by structural brain imaging and neuropsychological examination. OBJECTIVE: To investigate, using positron emission tomography (PET), the in vivo changes in regional cerebral uptake of 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) and regional cerebral blood flow (rCBF) in patients with persistent symptoms following mild head trauma. METHODS: Five patients with mild head trauma and five age and education matched healthy controls were imaged using FDG-PET to measure differences in resting regional cerebral glucose metabolism. Oxygen-15 labelled water (H(2)(15)O)-PET was also used to measure group differences in rCBF changes during a spatial working memory task. In addition, neuropsychological testing and self report of dysexecutive function and post-concussion symptoms were acquired to characterise the sample. RESULTS: There was no difference between patients and controls in normalised regional cerebral FDG uptake in the resting state in frontal and temporal regions selected a priori. However, during the spatial working memory task, patients had a smaller increase in rCBF than controls in the right prefrontal cortex. CONCLUSIONS: Persistent post-concussive symptoms may not be associated with resting state hypometabolism. A cognitive challenge may be necessary to detect cerebral changes associated with mild head trauma.     

What can eye movements tell us about Symbol Digit substitution by patients with schizophrenia?

Substitution tests are sensitive to cognitive impairment and reliably discriminate patients with schizophrenia from healthy individuals better than most other neuropsychological instruments. However, due to their multifaceted nature, substitution test scores cannot pinpoint the specific cognitive deficits that lead to poor performance. The current study investigated eye movements during performance on a substitution test in order to better understand what aspect of substitution test performance underlies schizophrenia-related impairment. Twenty-five patients with schizophrenia and 25 healthy individuals performed a computerized version of the Symbol Digit Modalities Test while their eye movements were monitored. As expected, patients achieved lower overall performance scores. Moreover, analysis of participants' eye movements revealed that patients spent more time searching for the target symbol every time they visited the key area. Patients also made more visits to the key area for each response that they made. Regression analysis suggested that patients' impaired performance on substitution tasks is primarily related to a less efficient visual search and, secondarily, to impaired memory.     

Premorbid child and family functioning as predictors of post-concussive symptoms in children with mild traumatic brain injuries

Study aim

This study sought to determine whether premorbid child and family functioning accounts for or moderates group differences in post-concussive symptoms following mild traumatic brain injury (TBI) in childhood.

Methods

This prospective, longitudinal cohort study recruited 8- to 15-year-old children, 186 with mild TBI and 99 with orthopedic injuries (OI), from consecutive emergency department admissions. Parents and children rated post-concussive symptoms within 3 weeks of injury and at 1, 3, and 12 months post injury. Parents also provided retrospective ratings of pre-injury symptoms, as well as of premorbid child behavioral adjustment, overall family functioning, and other stressors and resources in the family environment.

Results

Children with mild TBI reported more post-concussive symptoms than those with OI, as did their parents, although premorbid child behavioral adjustment and symptoms also were significant predictors of post-concussive symptoms. Group differences in somatic symptoms as reported by parents were more pronounced among children from families that were higher functioning and had more environmental resources.

Discussion

Mild TBI during childhood results in more post-concussive symptoms than OI, even after children's premorbid adjustment is taken into account. Counter to expectations, post-concussive symptoms following mild TBI may actually be more apparent among children from higher-functioning families with greater resources.     

Early HIV-related neuropsychological impairment: relationship to stage of viral infection

Sixty male outpatients with no past neuropsychiatric history were examined for evidence of early HIV-related neuropsychological impairment. Significant cognitive deficit, as measured by the RAVLT and WAIS-R Digit Symbol Substitution tests, and moderate correlation with indices of immune function, were observed in a group of patients with AIDS-Related Complex [ARC]. Patients with asymptomatic HIV-infection demonstrated no significant differences in performance compared to a group of HIV-seronegative controls. No significant group differences in age, education, predicted-IQ or self-rated depression and anxiety were observed. These results support the hypothesis that HIV-related cognitive disturbance occurs within the context of immunosuppression.